Ultrahigh pressure apparatus



June 30, 1970 sHulcHlRQ TAKAHASH| ET AL 3,517,413

ULTRAHIGH PRESSURE APPARATUS Filed Aug. 15, 1967 s sheetssheet 1 June 30, 1970 sHulcHlRo TAKAHASHI ETAI- 3,517,413

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ULTRHIGH PRESSURE APPARATUS Filed Aug. 15, 1967 Y. 5 sheets+sheet s United States Patent O 3,517,413 ULTRAHIGH PRESSURE APPARATUS Shuichiro Takahashi and Naoto Asam, Omiya, Japan, as-

signors to Mitsubishi Atomic Power Industries, Inc., Tokyo, Japan Filed Aug. 15, 1967, Ser. No. 660,712 Claims priority, application Japan, Feb. 28, 1967, 42/ 12,302 Int. Cl. B29c 3/00; B29g I/00 U.S. Cl. 18-16 10 Claims ABSTRACT F THE DISCLOSURE The apparatus is a plural polyhedron anvil type ultrahigh pressure apparatus. An outer anvil group consists of plural anvils and each anvil is formed so that its inner space forms an octahedron, a hexahedron or a tetra hedron. The inner anvil group also consists of a plurality of anvils and each anvil is shaped so that the external form of the inner anvil group fits into the internal space, formed by its outer anvil group and the internal space formed by the inner anvil group forms an octahedron, a hexahedron or a tetrahedron. The inner anvil group surrounds the high compression zone in three dimensions and the outer anvil group surrounds the inner anvil group in three dimensions. The outer anvil group is sealed with thin soft elastic shell material and compressed by the pressurized hydraulic liquid.

This invention relates to ultrahigh pressure apparatus and more particularly to multi-anvil type high pressure apparatus. There have been two kinds of pressure generating systems in principle. The one is a piston-cylinder type and the other is an anvil type. Improved type or modified type apparatus of these two principles have been used up to date. Bridgmann anvil (opposed anvil) type, tetrahedral anvil type, hexahedral (cubic) anvil type and octahedral anvil type, etc., apparatus belong to the anvil type very high pressure apparatus. Furthermore, the following pressure generating mechanisms are used for the anvil type apparatus:

(1) Having a press mechanism corresponding to each direction of anvil movement.

(2) Consisting of a conically tapered container and the fitted anvils to convert the force-direction from uniaxial to specified multiaxial forces.

(3) Using a high pressure vessel as the container of the anvil system and high pressure hydraulic liquid. The anvil system consists of the anvil, anvil support and anvil guide which are assembled into a unitary structure having a simple configuration, and this assembled anvil is sealed with soft elastic materials such as rubber.

In this invention, the pressure generating mechanism belongs to the third case described above.

Bridgmann anvil using tungsten carbide as the anvil material is capable of generating pressure up to about l5() kb. The anvil of this type has disadvantageous characteristics such as small compressed volume, difficulty in egecting internal heating, pressure developed has poor uniformity and unidirectional stress` corresponding to the compressing direction. In ordinary tetrahedral anvil or hexahedral anvil type apparatus the generating pressure is suppressed up to about 80 to 12() kb. by the existence of the local stress concentration in the anvil materials and furthermore, operation mechanism of these types is somewhat complex.

Patented June 30, 1970 Usual simple octahedral, or cubic anvil type apparatus using hydrostatic pressure acting on the outside of sealed anvil assembly having the third pressure generating mechanism as described above, can generate pressure up to kb. In these simple types, however, the local stress concentration in the anvil material also occur', and this causes deformation or fracture on the anvil material.

An object of rthis invention is to extend the generating pressure limit, by avoiding the mechanical defects of the usual apparatus. The invention provides a method of using a small number of supplies and relatively easy operation. Therefore, the multianvil type of very high pressure, for example, as in the case of an octahedron anvil combined with a hexahedron anvil, consists of a plurality of anvil group and the group of the outer anvils has the same number of faces as the number of the inner regular polyhedron space and is in conformity with a group of the inner anvils which have outer surface having the regular polyhedron shape. These inner anvil groups have a regular polyhedron in their inner surface. These combinations of regular polyhedrons are able to combine repeatedly, and a two stage combination is the least number in the combination.

The shape of the outermost anvil group is formed as a rotated axial symmetric shape such as a sphere, ellipsoid or cylinder. These anvil assemblies are sealed with soft elastic shell made from compressible materials such as organic materials like rubber, and subjected to hydraulic liquid pressure.

By increasing the hydrostatic component of environmental pressure in the innermost anvil material and the decrement of shear stress, the generating pressure range was extended with the increasing strength of anvil material. These are realized by the following structures to be described.

According to the multistage combination of regular polyhedral anvil groups, the inner anvil is compressed by the multiaxial compressive stress caused by compression of the outer anvils. This effect is accompanied with intensifying effect at each stage.

The stress field of the inner compressed anvil inclines to the higher hydrostatic compressive stress field. Consequently an ultrahigh pressure is obtainable and dissipation of anvil material is rare. Then, the ultrahigh pressure apparatus concerning this invention is explained by a following embodiment.

ULTRAHIGH PRESSURE APPARATUS For better understanding of the invention, reference is made to the following description of a representative embodiment thereof and to the accompanying drawings wherein:

FIG. 1 shows the horizontal cross section of an embodiment of the ultrahigh pressure apparatus.

FIG. 2 and FIG. 3 show the three dimensional configurations, mainly describing the periphery of the 2nd anvils of the apparatus. The correlation between the lst, 2nd and 3rd anvils are well explained by these figures.

FIG. 4 is the magnified view of a 2nd anvil.

FIG. 5 shows the magnified view of a 3rd anvil which is the case if three component anvils were used.

FIG. 6 is a schematic diagram of the radial direction of each element of the apparatus shown in FIG. 1.

FIG. 7 and FIG. 8 are views of the modified examples of 2nd or 3rd anvil shown in FIG. 4 and FIG. 5, respectively.

Referring to the drawings, FIG. l illustrates the cross section of an apparatus of a 8-6-8 facetted polyhedron combination as each three stage of anvils form the regular polyhedron in an inner space respectively.

First stage or outermost anvils 1 are composed of eight identical pieces (four pieces of the rst stage anvils are shown in FIG. 1), and form a regular octahedron in its inner space made by the cutting of a part of the anvil. The regular octahedron corresponding to the space is divided to six identical pieces 2 (one of which is shown in FIG. 4) and form the group of second stage anvils. The group of second stage anvils 2, which has the outside shape of a regular octahedron, is conformed with the inner regular octahedron of the rst stage anvils (refer to FIG. 2) and form a regular hexahedron (cubic) in its inner space made by cutting an edge of the anvil.

The regular hexahedron is divided into eight identical pieces 3 (this one division is shown in FIG. 5), forming the group of third stage anvils. The group of third stage anvils 3 which has the outside shape of a regular hexahedron, are confirmed with the inner regular hexahedron of second stage anvils, and form a regular octahedron in its inner space made by cutting a part of an edge of the anvil.

Plastic pressure medium 0 containing a specimen is set in the innermost regular octahedron. In this Way, important characteristics of the apparatus according to this invention are characterized by the complex multistage combination of a regular polyhedron such as the combination of a regular octahedron and a regular hexahedron. FIG. l also illustrates the case of a 6-8-6 polyhedron combination.

In the case of a 6-8-6 polyhedron combination, these circumstances are considered by the conversion of the octahedron to hexahedron, and hexahedron to octahedron and the number of anvils each other in above sentences. The same stages of anvils are arranged with the prescribed space which is necessary to effect compression of each other, so each stage of the anvil assembly can shrink into the center homogeneously and simultaneously to compress the pressure medium. The center 0 of each inner space made by each stage of anvil assembly correspond to each other.

Transmission of the compressed force is performed through the close contact of each stage of the anvil assembly. The advancing direction of each stage anvil (the conversion direction of compressed force) is changed by 5444 at one stage. In crystallographic terminology, the angle agreed with the angle made by lll and 100 direction. The generating pressure is inversely proportionate to the ratio 0f inner surface area and outer surface area in principle, and reaches its maximum value at the inner surface of the last stage anvil.

Quasi-hydrostatic pressure acts on the plastic pressure medium occupied by the center core 0. The force acting on the one of the first stage anvil 1 is separated into the three directions, and act on the three second stage anvils 2, respectively.

One of the second stage anvils 2 is propped up by the compressive force of four rst stage anvils. Consequently, the composed force compresses one of the surface of cube which is constituted by the group of second stage anvils.

The force acting on one of the second stage anvils 2 is separated into four directions and acts on the four third stage anvils 3, respectively. One of the third stage anvils 3 is propped up by the compressive force of three second anvils 2. The force developed compresses one of the surfaces of a regular octahedron which is constituted by the group of third stage anvils.

The pressure transmitter 4 and 4 organized by the inorganic plastic materials or organic plastic material is disposed between the first, second and third stage anvils to lubricate the mutual movement for compressing toward the center, to insulate electrically each other, and to eliminate the component of shearing stresses in the anvil materials.

The mutual gaps 5 between the same anvils is provided to make possible the advance of the anvils and to generate the pressure.

If the circumstances require, it is possible to insert the spacer 5 made by porous plastic materials in the gaps 5 for increasing the environment pressure of anvil material and to develop adequate space.

The anvil guides 8 of the first stage anvil and the insulating plate 6 are established to avoid the pressing out of the soft elastic shell 7 into the anvil gaps, and it is useful to guide the anvils at the setting and compressing and to insulate electrically the anvils from each other. These above assemblies are sealed with the soft elastic shell 7, and compressed by the hydraulic liquid 9. The structure of the embodiment is enumerated from center 0 to outside as follows:

Plastic pressure medium 0 containing the specimen, third stage anvils 3, pressure transmitter 4', second stage anvils 2, pressure transmitter 4, rst stage anvils, insulating plate 6 anvil guides I8, soft elastic shell 7 and hydraulic liquid 9. This hydraulic liquid is able to pressurize up to 10,000 kg./cim.2 or so a pressure vessel to generate an ultrahigh pressure at the center space 0.

The cartridge 10 containing the second and third stage anvils and pressure transmitter 44 and/or 10" containing the third stage anvils and pressure transmitter 4 can establish to change the anvils and samples as a unit necessary for improving the operation eiciency. In this case, the structure of the assembly is the following:

Plastic pressure transmitter 0 containing the specimen, third stage anvils 3, pressure transmitter 4', cartridge 10', second stage anvil 2, pressure transmitter 4, cartridge 10, first stage anvil 1 insulating plate 6, anvil guide 8, soft elastic shell 7 and hydraulic liquid 9. Two stage anvils such as 8-6, 6-8 or other kinds of polychoctron combinations are the most simple combinations of the anvils.

A pressure medium is inserted in the regular polyhedron of the core formed by the group of the second stage anvils in these cases.

Furthermore, a 8-6-8 polyhedron combination is the case using the third stage anvils of eight identical anvils put into the space of the regular octahedron as shown in FIG. 1.

It is possible to make the other combinations of 6-8-6, 8-6-86 or 6-8-6-8 or the like.

The limit generating pressure can be increased by the many combinations of anvils but the complexity of operation and setting of the apparatus is accompanied. However, operation eiciency can be improved 'by using the cartridge as previously described.

To avoid the deformation and fracture of anvil material due to the stress concentration, the sharp edges may be lapped or ground as illustrated in FIG. 7 or 8, and if it is necessary to hold the original anvil shape, it can be compensated by putting on the materials little softer than the original anvil materials.

This improvement is carried out by making equal the ratio of the outer area to the inner area. The shape of the specimen in the pressure medium can be reformed complied with the purpose of experiment by this improvement.

Another combination consisted of the tetrahedron is mentioned, the combination of 6-4, 4 4, 8-6-4, 6-4-4, 6-8-6-4 polyhedron are the possible combinations.

And a fresh combination combined with trisoctahedron is possible, however, the setting of the assembly will be complicated.

The function of the apparatus concerning this invention is considered as follows: The relation among the elements is denoted as where Po is the pressure of hydraulic liquid which acts on the outer surface of the anvil assembly, So is the averaged outer surface area of the anvil assembly, Si is the averaged inner surface area of the anvil assembly where the pressure medium is inserted, Pi is the generating pressure and f is the loss factor. This loss factor f is the function affected by the structure of apparatus, stationing of the spacer, pressure of Pz' and Po and the ratio of the area So/Sz'. However, the loss factor f is considered to be the function of the maximum generating pressure. Pimm in was determined qualitatively when the whole structure was established.

The loss factor f contains not only the true mechanical loss but the term due to the compressive force toward the center converted to a multiaxial force for increasing the environmental pressure in the anvil materials.

This matter is considered to be the only disadvantage, but this loss is the necessary and important factor for getting ultrahigh pressure because the strength of the anvil material is restricted at the present time.

In this invention, the compressive force acts from the first stage anvils to inner stage anvils, the vector of the force is changed accordingly, and separated to the same quantitative multiaxial compressive force. This multiaxial compressive force acts on the next inner stage anvils. Therefore, a large part of the loss factor is considered to be used to reinforce the anvils.

The advancing direction of the each stage anvil changes by 5444, respectively. This angle is near the direction of the shear stress in the case of simple compression or tension. Thus according to the formation of the anvil combination in this invention, the fracture of an anvil due to shear stress can be prevented. The maximum pressure at the last stage is extended due to introduction of these mechanisms, and it offers an economical method because the low grade material is useable as the anvil when the required pressure is constant.

FIG. 6 shows a schematic graph illustratiing the state of intensification and transmission of pressure at each stage.

The graph shows a case in which the last stage of anvils (the third stage anvil in the embodiment) enters into the plastic range of the material.

Namely, the line of intensification curved at point t existed in the last stage anvil and this indicates the plastic range extending from a to t without fracture. In this type of apparatus, pressure intenification still remains in the elasto-plastic range of the anvil. The pressure transmitter is able to have an intensification effect so far as the anvil doesnt fail.

The line between b and c and d and e inclined in this case.

EXAMPLE I 8-6 polyhedron combination anvil type ultrahigh pressure apparatus using a high strength die steel having the tensile strength of 215 lag/mim.2 as the material of first stage anvil, and tungsten carbided with cobalt alloy as the material of second stage anvil, was manufactured. The ratio of innermost and outermost average diameters was twenty, thus the area ratio was four hundred. The pressure calibration point of bismuth (25 kb., 88 kb.) and lead (1611 kb.) reappeared accurately. The generating pressure up to 195 kb. was attained without fracture of an anvil, and this was confirmed by the extrapolation of the calibration curve, and the loss factor f was equal to 3.6 in this case. A pyrophillite cubic 1.25 times larger than a side of the square surface of second stage anvil was used as a pressure medium, and the combination of pyrophillite plates and Teflon sheets and molybdenum disulfide powder was used as the pressure transmitter.

EXAMPLE II 8-6-8 polyhedron combination anvil type ultrahigh pressure apparatus which consists of the eight identical pieces of cubic like anvils adjusted to an inner space of a 8-6 polyhedron combination anvil type apparatus as described in embodiment (I) was manufactured. The third anvil was made of tungsten carbide 3% cobalt alloy. The ratio of the innermost and outermost average diameters was thirty, thus the area ratio was nine hundred. The generation of pressure up to 270 kb. is confirmed by the extrapolation of calibration without fracture. The last stage anvils were somewhat deformed but usable repeatedly, and the lost factor fwas equal to 6.5 in this case. The pressure transmitter between the first and the second stage anvils was same as the case (I) and that between the second and third stage anvils was constructed with the special compressed paper and Teflon sheets.

EXAMPLE III 6-8 polyhedron combination anvil type ultrahigh pressure apparatus using a high strength die steel as the material of first stage anvil and tungsten carbide 5% cobalt alloy as the material of second stage anvil. The ratio of the innermost and outermost average diameters Was twenty, thus the area ratio was four hundred. The generation of pressure up to 210 kb. was repeatedly confirmed by the extrapolation of calibration, and loss factor f was equal to 3.85 in this case. A pyrophillite octahedron 1.25 times larger than a side of the regular triangle surface of a second stage anvil was used as the pressure medium, and the combination of a pyrophillite plate and Teflon sheets was used as the pressure transmitter.

EXAMPLE IV 6-8 polyhedron combination anvil type apparatus using a hot die steel as the material of the first stage anvil, and high carbon steel having a Vickers hardness of about 950 VHN as the second anvils. A pressure up to kb. was attained without fracture of the second anvil materials.

EXAMPLE V In the case of a 8-6-8 polyhedron combination anvil type apparatus as described in embodiment (II), the cartridge made by a nylon net was used containing a pressure transmitter, the group of the last stage anvil, specimen and spacer. It is very easy to exchange work of the specimen assembly.

What we claim is:

1. A polyhedral anvil type apparatus for generating ultrahigh pressures comprising, an anvil assembly including at least two anvil members nested one within another, the innermost anvil member defining a vmr-king space, and a shell member of soft resilient material for henmetilcally sealing and transmitting external hydrostatic pressure to the anvil assembly, and wherein the outermost anvil member is in the form of a body having symmetry of rotation, each of said anvil members having a predetermined internal space in the form of a regular polyhedron and includes a plurality of anvil elements identical in shape to each other and equal in number to the facets of the internal space in which it is nested, and said plurality of anvil elements of each anvil member in their assembled position provide an outer surface complementary in shape to the internal space in which they are nested and have inner end faces providing respective facets of the internal polyhedral space defined by the anvil member.

2. An apparatus according to claim 1, in which said internal spaces alternately have the form of a regular octahedron and a cube.

3. An apparatus according to claim 2, in which the outer space has the form of a regular octahedron.

4. An apparatus according to claim 2, in which the outermost space has the form of a cube.

5. An apparatus according to claim 1, in which said internal spaces alternately have the form of a cube and a regular tetrahedron.

6. An apparatus according to claim 5, in which the outermost space is in the form of a cube.

n 7 A 8 7. An apparatus according to claim 5, in which the Y References Cited outermost space is in the form of a regular tetrahedron. UNITED STATES PATENTS 8. Ari apparatus according to claim 1, in which a layer of soft resilient material is interposed between each pair 2,947,034 8/ 1960 Wentorf. of adjacent anvil members. 5 3,154,619 10/ 1964 Brayman et al.

9. An apparatus according to claim 8, in which at least 3,231,935 12/ 1966 Brayman.

the innermost anvil member and an associated flexible 3,261,057 7/ 1966 Contre,

layer is enclosed by a flexible cartridge.

10. An apparatus according to claim 1, in which the WILBUR L- MCBAY, Pflmal'y Examlnelinnermost anvil member in use is stressed in its elasto- 10 plastic range. 

